The principle is that the power drives the sound barrel with small protrusions on the surface to rotate at a constant speed. When the protrusions pass the soundboard sound bar, the reed will be stirred to slowly lift it first, and then suddenly lower it, causing the reed to rotate. The piece vibrates according to the set vibration frequency and emits the set sound. The soundboard part of the music box is made from a piece of elastic steel plate cut into thin strips of the same length but varying thickness. The thickness varies according to the set vibration frequency. A bump on the speaker is equivalent to a note on the musical score. A sound tube rotates according to the regularly set bumps, and the bumps pass across the edge of the soundboard. Due to the different bumps, the pronunciation is different, coupled with the damping effect, the sound tube rotates at a uniform speed. The cycle time for ordinary movements is generally between 8 and 17 seconds, which is enough to express the final part of a piece of music; high-end music boxes generally cycle between 30 seconds and 8 minutes.